#!/usr/bin/env bash
# snap-sync
# https://github.com/wesbarnett/snap-sync
# Copyright (C) 2016-2021 Wes Barnett

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,

# -------------------------------------------------------------------------

# Takes snapshots of each snapper configuration. It then sends the snapshot to
# a location on an external drive. After the initial transfer, it does
# incremental snapshots on later calls. It's important not to delete the
# snapshot created on your system since that will be used to determine the
# difference for the next incremental snapshot.

set -o errtrace

version="0.7"
name="snap-sync"

printf "\nsnap-sync version %s, Copyright (C) 2016-2021 Wes Barnett\n" "$version"
printf "snap-sync comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it under certain conditions. See the license for more information. \n\n"

# The following line is modified by the Makefile or
# find_snapper_config script
SNAPPER_CONFIG=/etc/sysconfig/snapper

donotify=0
if ! command -v notify-send &>/dev/null; then
    donotify=1
fi

doprogress=0
if ! command -v pv &>/dev/null; then
    doprogress=1
fi

error() {
    printf "==> ERROR: %s\n" "$@"
    notify_error 'Error' 'Check journal for more information.'
} >&2

die() {
    error "$@"
    exit 1
}

traperror() {
    printf "Exited due to error on line %s.\n" "$1"
    printf "exit status: %s\n" "$2"
    printf "command: %s\n" "$3"
    printf "bash line: %s\n" "$4"
    printf "function name: %s\n" "$5"
    exit 1
}

trapkill() {
    die "Exited due to user intervention."
}

trap 'traperror ${LINENO} $? "$BASH_COMMAND" $BASH_LINENO "${FUNCNAME[@]}"' ERR
trap trapkill SIGTERM SIGINT

usage() {
    cat <<EOF
$name $version
Usage: $name [options]

Options:
 -c, --config <config>    snapper configuration to backup
 -d, --description <desc> snapper description
 -h, --help               print this message
 -n, --noconfirm          do not ask for confirmation
 -k, --keepold            keep old incremental snapshots instead of deleting them
                          after backup is performed
 -p, --port <port>        remote port; used with '--remote'.
 -q, --quiet              do not send notifications; instead print them.
 -r, --remote <address>   ip address of a remote machine to backup to
 --sudo                   use sudo on the remote machine
 -s, --subvolid <subvlid> subvolume id of the mounted BTRFS subvolume to back up to
 -u, --UUID <UUID>        UUID of the mounted BTRFS subvolume to back up to

See 'man snap-sync' for more details.
EOF
}

ssh=""
sudo=0
while [[ $# -gt 0 ]]; do
    key="$1"
    case $key in
    -d | --description)
        description="$2"
        shift 2
        ;;
    -c | --config)
        selected_configs="$2"
        shift 2
        ;;
    -u | --UUID)
        uuid_cmdline="$2"
        shift 2
        ;;
    -s | --subvolid)
        subvolid_cmdline="$2"
        shift 2
        ;;
    -k | --keepold)
        keep="yes"
        shift
        ;;
    -n | --noconfirm)
        noconfirm="yes"
        shift
        ;;
    -h | --help)
        usage
        exit 1
        ;;
    -q | --quiet)
        donotify=1
        shift
        ;;
    -r | --remote)
        remote=$2
        shift 2
        ;;
    -p | --port)
        port=$2
        shift 2
        ;;
    --sudo)
        sudo=1
        shift
        ;;
    *)
        die "Unknown option: '$key'. Run '$name -h' for valid options."
        ;;
    esac
done

notify() {
    for u in $(users | tr ' ' '\n' | sort -u); do
        sudo -u "$u" DISPLAY=:0 \
            DBUS_SESSION_BUS_ADDRESS="unix:path=/run/user/$(sudo -u "$u" id -u)/bus" \
            notify-send -a $name "$1" "$2" --icon="dialog-$3"
    done
}

notify_info() {
    if [[ $donotify -eq 0 ]]; then
        notify "$1" "$2" "information"
    else
        printf '%s\n' "$1: $2"
    fi
}

notify_error() {
    if [[ $donotify -eq 0 ]]; then
        notify "$1" "$2" "error"
    else
        printf '%s\n' "$1: $2"
    fi
}

[[ $EUID -ne 0 ]] && die "Script must be run as root. See '$name -h' for a description of options"
! [[ -f $SNAPPER_CONFIG ]] && die "$SNAPPER_CONFIG does not exist."

description=${description:-"latest incremental backup"}
uuid_cmdline=${uuid_cmdline:-"none"}
subvolid_cmdline=${subvolid_cmdline:-"5"}
noconfirm=${noconfirm:-"no"}

if [[ -z $remote ]]; then
    if ! command -v rsync &>/dev/null; then
        die "--remote specified but rsync command not found"
    fi
fi

if [[ $uuid_cmdline != "none" ]]; then
    if [[ -z $remote ]]; then
        notify_info "Backup started" "Starting backups to $uuid_cmdline subvolid=$subvolid_cmdline..."
    else
        notify_info "Backup started" "Starting backups to $uuid_cmdline subvolid $subvolid_cmdline at $remote..."
    fi
else
    if [[ -z $remote ]]; then
        notify_info "Backup started" "Starting backups. Use command line menu to select disk."
    else
        notify_info "Backup started" "Starting backups. Use command line menu to select disk on $remote."
    fi
fi

if [[ -n $remote ]]; then
    ssh="ssh $remote"
    if [[ -n $port ]]; then
        ssh="$ssh -p $port"
    fi
    if [[ $sudo -eq 1 ]]; then
        ssh="$ssh sudo"
    fi
fi

if [[ "$($ssh findmnt -n -v --target / -o FSTYPE)" == "btrfs" ]]; then
    EXCLUDE_UUID=$($ssh findmnt -n -v -t btrfs --target / -o UUID)
    TARGETS=$($ssh findmnt -n -v -t btrfs -o UUID,TARGET --list | grep -v "$EXCLUDE_UUID" | awk '{print $2}')
    UUIDS=$($ssh findmnt -n -v -t btrfs -o UUID,TARGET --list | grep -v "$EXCLUDE_UUID" | awk '{print $1}')
else
    TARGETS=$($ssh findmnt -n -v -t btrfs -o TARGET --list)
    UUIDS=$($ssh findmnt -n -v -t btrfs -o UUID --list)
fi

declare -a TARGETS_ARRAY
declare -a UUIDS_ARRAY
declare -a SUBVOLIDS_ARRAY

i=0
for x in $TARGETS; do
    SUBVOLIDS_ARRAY[i]=$($ssh btrfs subvolume show "$x" | awk '/Subvolume ID:/ { print $3 }')
    TARGETS_ARRAY[i]=$x
    i=$((i + 1))
done

i=0
disk=-1
disk_count=0
for x in $UUIDS; do
    UUIDS_ARRAY[i]=$x
    if [[ $x == "$uuid_cmdline" && ${SUBVOLIDS_ARRAY[$((i))]} == "$subvolid_cmdline" ]]; then
        disk=$i
        disk_count=$((disk_count + 1))
    fi
    i=$((i + 1))
done

if [[ ${#UUIDS_ARRAY[$@]} -eq 0 ]]; then
    die "No external btrfs subvolumes found to backup to. Run '$name -h' for more options."
fi

if [[ $disk_count -gt 1 ]]; then
    printf "Multiple mount points were found with UUID %s and subvolid %s.\n" "$uuid_cmdline" "$subvolid_cmdline"
    disk="-1"
fi

if [[ $disk == -1 ]]; then
    if [[ $disk_count == 0 && $uuid_cmdline != "none" ]]; then
        error "A device with UUID $uuid_cmdline and subvolid $subvolid_cmdline was not found to be mounted, or it is not a BTRFS device."
    fi
    if [[ -z $ssh ]]; then
        printf "Select a mounted BTRFS device on your local machine to backup to.\nFor more options, exit and run '%s -h'.\n" "$name"
    else
        printf "Select a mounted BTRFS device on %s to backup to.\nFor more options, exit and run '%s -h'.\n" "$remote" "$name"
    fi
    while [[ $disk -lt 0 || $disk -gt $i ]]; do
        for x in "${!TARGETS_ARRAY[@]}"; do
            printf "%4s) %s (uuid=%s, subvolid=%s)\n" "$((x + 1))" "${TARGETS_ARRAY[$x]}" "${UUIDS_ARRAY[$x]}" "${SUBVOLIDS_ARRAY[$x]}"
        done
        printf "%4s) Exit\n" "0"
        read -e -r -p "Enter a number: " disk
        if ! [[ $disk == ?(-)+([0-9]) ]] || [[ $disk -lt 0 || $disk -gt $i ]]; then
            printf "\nNo disk selected. Select a disk to continue.\n"
            disk=-1
        fi
    done
    if [[ $disk == 0 ]]; then
        exit 0
    fi
    disk=$((disk - 1))
fi

selected_subvolid="${SUBVOLIDS_ARRAY[$((disk))]}"
selected_uuid="${UUIDS_ARRAY[$((disk))]}"
selected_mnt="${TARGETS_ARRAY[$((disk))]}"
printf "\nYou selected the disk with uuid=%s, subvolid=%s.\n" "$selected_uuid" "$selected_subvolid"
if [[ -z $ssh ]]; then
    printf "The disk is mounted at '%s'.\n" "$selected_mnt"
else
    printf "The disk is mounted at '%s:%s'.\n" "$remote" "$selected_mnt"
fi

# shellcheck source=/dev/null
source "$SNAPPER_CONFIG"

if [[ -z $selected_configs ]]; then
    printf "\nInteractively cycling through all snapper configurations...\n"
fi
selected_configs=${selected_configs:-$SNAPPER_CONFIGS}

declare -a BACKUPDIRS_ARRAY
declare -a MYBACKUPDIR_ARRAY
declare -a OLD_NUM_ARRAY
declare -a OLD_SNAP_ARRAY
declare -a NEW_NUM_ARRAY
declare -a NEW_SNAP_ARRAY
declare -a NEW_INFO_ARRAY
declare -a BACKUPLOC_ARRAY
declare -a CONT_BACKUP_ARRAY

# Initial configuration of where backup directories are
i=0
for x in $selected_configs; do

    if [[ "$(snapper -c "$x" list --disable-used-space -t single | awk '/'"subvolid=$selected_subvolid, uuid=$selected_uuid"'/ {cnt++} END {print cnt}')" -gt 1 ]]; then
        error "More than one snapper entry found with UUID $selected_uuid subvolid $selected_subvolid for configuration $x. Skipping configuration $x."
        continue
    fi

    if [[ "$(snapper -c "$x" list --disable-used-space -t single | awk '/'$name' backup in progress/ {cnt++} END {print cnt}')" -gt 0 ]]; then
        printf "\nNOTE: Previous failed %s backup snapshots found for '%s'.\n" "$name" "$x"
        if [[ $noconfirm == "yes" ]]; then
            printf "'noconfirm' option passed. Failed backups will not be deleted.\n"
        else
            read -e -r -p "Delete failed backup snapshot(s)? (These local snapshots from failed backups are not used.) [y/N]? " delete_failed
            while [[ -n $delete_failed && $delete_failed != [Yy]"es" &&
                $delete_failed != [Yy] && $delete_failed != [Nn]"o" &&
                $delete_failed != [Nn] ]]; do
                read -e -r -p "Delete failed backup snapshot(s)? (These local snapshots from failed backups are not used.) [y/N] " delete_failed
                if [[ -n $delete_failed && $delete_failed != [Yy]"es" &&
                    $delete_failed != [Yy] && $delete_failed != [Nn]"o" &&
                    $delete_failed != [Nn] ]]; then
                    printf "Select 'y' or 'N'.\n"
                fi
            done
            if [[ $delete_failed == [Yy]"es" || $delete_failed == [Yy] ]]; then
                # explicit split list of snapshots (on whitespace) into multiple arguments
                # shellcheck disable=SC2046
                snapper -c "$x" delete $(snapper -c "$x" list --disable-used-space | awk '/'$name' backup in progress/ {print $1}')
            fi
        fi
    fi

    SNAP_SYNC_EXCLUDE=no

    if [[ -f "/etc/snapper/configs/$x" ]]; then
        # shellcheck source=/dev/null
        source "/etc/snapper/configs/$x"
    else
        die "Selected snapper configuration $x does not exist."
    fi

    if [[ $SNAP_SYNC_EXCLUDE == "yes" ]]; then
        continue
    fi

    printf "\n"

    old_num=$(snapper -c "$x" list --disable-used-space -t single | awk '/'"subvolid=$selected_subvolid, uuid=$selected_uuid"'/ {print $1}')
    old_snap=$SUBVOLUME/.snapshots/$old_num/snapshot

    OLD_NUM_ARRAY[i]=$old_num
    OLD_SNAP_ARRAY[i]=$old_snap

    if [[ -z $old_num ]]; then
        printf "No backups have been performed for '%s' on this disk.\n" "$x"
        read -e -r -p "Enter name of subvolume to store backups, relative to $selected_mnt (to be created if not existing): " mybackupdir
        printf "This will be the initial backup for snapper configuration '%s' to this disk. This could take awhile.\n" "$x"
        BACKUPDIR="$selected_mnt/$mybackupdir"
        $ssh test -d "$BACKUPDIR" || $ssh btrfs subvolume create "$BACKUPDIR"
    else
        mybackupdir=$(snapper -c "$x" list --disable-used-space -t single | awk -F"|" '/'"subvolid=$selected_subvolid, uuid=$selected_uuid"'/ {print $5}' | awk -F "," '/backupdir/ {print $1}' | awk -F"=" '{print $2}')
        BACKUPDIR="$selected_mnt/$mybackupdir"
        $ssh test -d "$BACKUPDIR" || die "%s is not a directory on %s.\n" "$BACKUPDIR" "$selected_uuid"
    fi
    BACKUPDIRS_ARRAY[i]="$BACKUPDIR"
    MYBACKUPDIR_ARRAY[i]="$mybackupdir"

    printf "Creating new local snapshot for '%s' configuration...\n" "$x"
    new_num=$(snapper -c "$x" create --print-number -d "$name backup in progress")
    new_snap=$SUBVOLUME/.snapshots/$new_num/snapshot
    new_info=$SUBVOLUME/.snapshots/$new_num/info.xml
    sync
    backup_location=$BACKUPDIR/$x/$new_num/
    if [[ -z $ssh ]]; then
        printf "Will backup %s to %s\n" "$new_snap" "$backup_location/snapshot"
    else
        printf "Will backup %s to %s\n" "$new_snap" "$remote":"$backup_location/snapshot"
    fi

    if ($ssh test -d "$backup_location/snapshot"); then
        printf "WARNING: Backup directory '%s' already exists. This configuration will be skipped!\n" "$backup_location/snapshot"
        printf "Move or delete destination directory and try backup again.\n"
    fi

    NEW_NUM_ARRAY[i]="$new_num"
    NEW_SNAP_ARRAY[i]="$new_snap"
    NEW_INFO_ARRAY[i]="$new_info"
    BACKUPLOC_ARRAY[i]="$backup_location"

    cont_backup="K"
    CONT_BACKUP_ARRAY[i]="yes"
    if [[ $noconfirm == "yes" ]]; then
        cont_backup="yes"
    else
        while [[ -n $cont_backup && $cont_backup != [Yy]"es" &&
            $cont_backup != [Yy] && $cont_backup != [Nn]"o" &&
            $cont_backup != [Nn] ]]; do
            read -e -r -p "Proceed with backup of '$x' configuration [Y/n]? " cont_backup
            if [[ -n $cont_backup && $cont_backup != [Yy]"es" &&
                $cont_backup != [Yy] && $cont_backup != [Nn]"o" &&
                $cont_backup != [Nn] ]]; then
                printf "Select 'Y' or 'n'.\n"
            fi
        done
    fi

    if [[ $cont_backup != [Yy]"es" && $cont_backup != [Yy] && -n $cont_backup ]]; then
        CONT_BACKUP_ARRAY[i]="no"
        printf "Not backing up '%s' configuration.\n" "$x"
        snapper -c "$x" delete "$new_num"
    fi

    i=$((i + 1))

done

# Actual backing up
printf "\nPerforming backups...\n"
i=-1
for x in $selected_configs; do

    i=$((i + 1))

    SNAP_SYNC_EXCLUDE=no

    if [[ -f "/etc/snapper/configs/$x" ]]; then
        # shellcheck source=/dev/null
        source "/etc/snapper/configs/$x"
    else
        die "Selected snapper configuration $x does not exist."
    fi

    cont_backup=${CONT_BACKUP_ARRAY[$i]}
    if [[ $cont_backup == "no" || $SNAP_SYNC_EXCLUDE == "yes" ]]; then
        notify_info "Backup in progress" "NOTE: Skipping $x configuration."
        continue
    fi

    notify_info "Backup in progress" "Backing up $x configuration."

    printf "\n"

    old_num="${OLD_NUM_ARRAY[$i]}"
    old_snap="${OLD_SNAP_ARRAY[$i]}"
    BACKUPDIR="${BACKUPDIRS_ARRAY[$i]}"
    mybackupdir="${MYBACKUPDIR_ARRAY[$i]}"
    new_num="${NEW_NUM_ARRAY[$i]}"
    new_snap="${NEW_SNAP_ARRAY[$i]}"
    new_info="${NEW_INFO_ARRAY[$i]}"
    backup_location="${BACKUPLOC_ARRAY[$i]}"

    if ($ssh test -d "$backup_location/snapshot"); then
        printf "ERROR: Backup directory '%s' already exists. Skipping backup of this configuration!\n" "$backup_location/snapshot"
        continue
    fi

    $ssh mkdir -p "$backup_location"

    if [[ -z $old_num ]]; then
        printf "Sending first snapshot for '%s' configuration...\n" "$x"
        if [[ $doprogress -eq 0 ]]; then
            btrfs send "$new_snap" | pv | $ssh btrfs receive "$backup_location" &>/dev/null
        else
            btrfs send "$new_snap" | $ssh btrfs receive "$backup_location" &>/dev/null
        fi
    else

        printf "Sending incremental snapshot for '%s' configuration...\n" "$x"
        # Sends the difference between the new snapshot and old snapshot to the
        # backup location. Using the -c flag instead of -p tells it that there
        # is an identical subvolume to the old snapshot at the receiving
        # location where it can get its data. This helps speed up the transfer.

        if [[ $doprogress -eq 0 ]]; then
            btrfs send -c "$old_snap" "$new_snap" | pv | $ssh btrfs receive "$backup_location"
        else
            btrfs send -c "$old_snap" "$new_snap" | $ssh btrfs receive "$backup_location"
        fi

        if [[ $keep == "yes" ]]; then
            printf "Modifying data for old local snapshot for '%s' configuration...\n" "$x"
            snapper -v -c "$x" modify -d "old snap-sync snapshot (you may remove)" -u "backupdir=,subvolid=,uuid=" -c "number" "$old_num"
        else
            printf "Deleting old snapshot for %s...\n" "$x"
            snapper -c "$x" delete "$old_num"
        fi

    fi

    if [[ -z $remote ]]; then
        cp "$new_info" "$backup_location"
    else
        if [[ -z $port ]]; then
            rsync -avzq "$new_info" "$remote":"$backup_location"
        else
            rsync -avzqe "ssh -p $port" "$new_info" "$remote":"$backup_location"
        fi
    fi

    # It's important not to change this userdata in the snapshots, since that's how
    # we find the previous one.

    userdata="backupdir=$mybackupdir, subvolid=$selected_subvolid, uuid=$selected_uuid"

    # Tag new snapshot as the latest
    printf "Tagging local snapshot as latest backup for '%s' configuration...\n" "$x"
    snapper -v -c "$x" modify -d "$description" -u "$userdata" "$new_num"

    printf "Backup complete for '%s' configuration.\n" "$x"

done

printf "\nDone!\n"

if [[ $uuid_cmdline != "none" ]]; then
    notify_info "Finished" "Backups to $uuid_cmdline complete!"
else
    notify_info "Finished" "Backups complete!"
fi